WASHINGTON — John Danforth has resigned as U.S. ambassador to the United Nations barely five months after he took office.

Danforth, 68, a Republican and former senator from Missouri, said in a letter to President Bush dated Nov. 22 that he and his wife wanted to return to St. Louis, NBC’s Andrea Mitchell reported Thursday. He will leave by Jan. 20, when Bush is to be sworn in for a second term, said Richard Grenell, a spokesman for the U.S. delegation to the United Nations.

Danforth, who has been described as frustrated with the slow-moving U.N. bureaucracy, had recently told friends that he was running out of patience, especially with the Security Council, whose deliberations he considered difficult, Mitchell reported.

In a speech last month in St. Louis, Danforth said that as a former senator, he was not accustomed to having a policy statement vetted by State Department bureaucrats and transformed into “mush” before he could issue it.

Unhappiness seen as mutual
A senior State Department official said Danforth’s decision was not surprising. He campaigned vigorously to succeed Colin Powell as secretary of state and was described as disappointed when Bush picked national security adviser Condoleezza Rice.

The White House, meanwhile, was unhappy with some of the positions Danforth, an ordained Episcopal minister, had taken at the United Nations, the official said, in particular his proposal that the agency create a committee on religion.

Officials at the White House confirmed that one reason Bush did not promote Danforth was that he was seen as inflexible and “sanctimonious,” Mitchell reported. But he is widely respected in Washington, having been tapped by presidents of both parties as a troubleshooter.

Danforth was sworn in as ambassador to the United Nations on July 1, succeeding Bush’s first ambassador, John Negroponte, who became ambassador to Iraq.

He has commented little on corruption in the U.N. oil-for-food program, which some U.S. legislators have blamed on U.N. Secretary-General Kofi Annan. He said only that everyone hoped that investigations by the United Nations and congressional panels would bring out the truth.

NBC’s Andrea Mitchell and Tamara Kupperman in Washington and Linda Fasulo in New York and Reuters contributed to this report.